The Sky Road represents an 'alternate future' to the other books, as its events diverge sharply from those in the other books after 2059, due to a choice made differently by one of the protagonists.
... the merit of good
works and transubstantiation (iv. 2), purgatory
(iv. 9), and the worship of saints (i. 13, ii. 9, iii. 6,
59). In other works, however, Thomas à ...